Adrian h



UNITED STATES PATENT OFFICE.

ADRIAN H. HOYT, OF MANCHESTER, NEW HAMPSHIRE, ASSIGNOR TC THE WHITNEYELECTRICAL INSTRUMENT COMPANY, OF SAME PLACE.

GALVANOM ETER.

SPECIFICATION forming part of Letters Patent No. 497,449, dated May 16,1893.

Application filed May 9, 1892- Serial No. 432,307. (No model.)

To all whom it may concern.-

Be it known that I, ADRIAN H. How, of Manchester, county ofHillsborough, State of New Hampshire, have invented an Improvement inGalvanometers, of which the followin g description, in connection withthe accompanying drawings, is a specification, like letters on thedrawings representing like parts.

My invention relates to a galvanometer and is shown as embodied in aninstrument to be connected directly with circuits carrying strongcurrents such for example as those employed for lighting or power.

The instrument comprises a solenoid which is preferably flattened oroval in transverse section and an armature or pole piece supported upona pivot near one end of the solenoid in such manner that the attractionof the current in the solenoid for the said core or armature tends tooscillate the latter both by the direct pull or attraction of thesolenoid for the body or mass of the core piece and also by the tendencywhich the solenoid coil has to place the core piece or needle with itslongitudinal axis in line with the longitudinal axis about which thesolenoid coil is wound.

The invention further consists in details of construction that will behereinafter specified.

Figure 1 is a front elevation of a galvanometer embodying thisinvention, and Fig. 2 a plan view of a portion thereof.

The instrument comprises a solenoid or coil a adapted to receive thecurrent to be measured said coil being preferably wound upon a flat tubethe open end of which is shown in Fig. 2. The said solenoid co-operateswith a core piece or armature b pivoted at b at a point near one end ofthe solenoid coila and at one side of the axis thereof, the main body ofsaid armature I) being normally at one side of its axis 12 and in linewith the tubular opening of the center piece on which the coil or iswound. The said core 6 is preferably of the shape shown in Fig. 1,namely, wider at its end remote from the pivot than adjacent to thepivot; the widened end thus extending toward orinto the tube of thesolenoid. Thus there is a greater mass in the armature at the partremote from its pivot than near its pivot and the remote part of themass is nearer the solenoid, so that the attraction ofthe latter has agreater efiect upon the part of the armature remote from the pivot thannear the pivot, and consequently tends to draw the part remote from thepivot into it and thus has a tendency to turn the said armature aboutits pivot or axis by the direct attraction of the solenoid or tendencyof the solenoid to draw a magnetic core piece toward its middle point.Further than this after the free end of the core piece has been drawndown into the solenoid the, tendency of the solenoid to bring a piece ofiron into the position in which the longer axis of said piece of iron isin line with the axis about which the solenoid coil is wound, also tendsto turn the said armature b from its normal substantiallyhorizontalposition toward the vertical position, or in other words, to produce afurther movement of said core piece about its axis at W.

In order that the eifect of the solenoid may produce different amountsof movement of said pole piece I) when the said solenoid is suppliedwith currents of different strength, so that the amount of movement maybe proportional to and indicative of the strength of the current, it isnecessary to provide a variable resistance to said movement which may bedone in various ways as is well known to those familiar with instrumentsof this kind. As herein shown the force of gravity is employed, the saidarmature I? being normally retained in the horizontal or retractedposition by means of a counterweight c which may be adjustable along thearm dconnected with the axis or rock shaft which constitutes the pivotalsupport for the armature, b. The

said counterweight 0 being nearly opposite the center of gravity of thearmature b produces a substantially constant resistance to the downwardoscillation of said armature, and in order to provide a variableresistance which increases as the armature departs from its normal orhorizontal position, its axis is provided with a second arm e which isvertically below the said axis when the armature b is in its normal orhorizontal position, and

thus has at that time no tendency to turn the said armature in eitherdirection, but when the said armature is turned the said arm 6 movesaway from vertical position and its weight 6 thus acts with increasingleverage to resist the oscillation of the armature as the latter movesfrom the horizontal toward the vertical position, and the said weightedarm moves from the vertical toward the horizontal position. The weight(2 may be adjustable along the arm 6 so as to vary its leverage and thusvary the amount of resistance to the movement of the armature. By thisconstruction the amount of movement of the armature will vary with thestrength of the current traversing the solenoid, and such movement maybe indicated by a suitable pointer fconnected with the axis or arbor ofthe armature and co operating with a suitably graduated scale f so thatthe position of the pointer relative to the said scale at any timeindicates the strength of the current then traversing the coil.

By the herein described construction an instrument capable of use withvery powerful currents is produced which at the same time has greatdelicacy of movement so that it responds readily to slight variations insaid currents, the instruments being far simpler, more compact, and lessexpensive than those heretofore commonly used for currents of suchcharacter in which the direct attraction of the solenoid for a core isemployed, requiring a comparatively long solenoid coil and core to givea sufficient range of movement to afford satisfactory indications.

I claim- 1. The combination of a solenoid coil with an armature pivotednear one end of its own length and near one end of said coil, andprovided with a counterbalancing weight as c and a weighted arm as e, 6opposing a vari able resistance to the oscillatory movement of saidarmature under the attraction from the said solenoid, substantially asdescribed.

2. The combination of the solenoid flat or oval in cross section, withthe armature pivoted at one end near one end of one side of the openingthrough the solenoid, the said armature being wider at its free end thanat its pivoted end, and provided with a retractor to oppose itsoscillatory movement produced by the attraction of the solenoid,substantially as described.

3. The combination of the solenoid, flat or oval in cross section withthe armature pivoted at one end near one end of one side' of the openingthrough the solenoid, and provided with a weighted arm opposing avariable resistance to its oscillatory movement, substantially asdescribed.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

ADRIAN Il. HOYT.

Vitnesses:

Jos. P. Llvnmnona, JAs. J. MALONEY.

